Automatic tuning device



Aug. 15, 1950 R. P. HAVlLAND AUTOMATIC TUNING DEVICE Filed March 29, 1949 2 R R. m OF 0 WW E L E, H D A l w 4 0 a. m 2 Wm m m P m s B A B I: R m 5 m H filo E% W S AF. PM.U N m Ao PS 8 m W Fla. 1

R.F. OUTPUT CAPACITY ROBERT I? HAV/LAND E p 2,518,470 A "1 1, I "AUTOMATIC TUNING DEVICE i havilandQSootimY- I V V hpplication March 29, 1949, 'seriamms g iz Claims. (Cl.:25(l -40)" q (Granted under the act of March 3, 1883 as ai'n'eruled April 30, 1928; 370 0. G. 7 51) i; jThe present inventionl. ielates to a utoinatic other objects and advantag es thereofiswill be tuning devices and more particularly to a device readily apparent from consideration of the. folfor automatically tuning aresonant'circuitto its lowing specification relating to the annexed -optimum operating pointand to maintain the drawing in which:

circuit atthat p 5 w Fig. 1 illustrates a circuit arrangement of one More specifi ally this nve tionv concerns a embodiment of the present invention as applied type of co ol c u t Suitable fOr cOntrOl 0f t to the tank circuitof .a radio frequency amplifier; direction of rotation of amotor for usages such and p as remote control of anlelement of a tuning cir- Fig. 2 shows a plurality of wave form i11 cuit. The means for controlling the circuit may 1 trating the operation of a portionqof the i be derived irom the deviation in frequency of a cult of Fig. 1.

radio frequency gn llbe s am l e a the Referring now to the drawings, there is shown motor y tune the m l r u of the amplifier in Fig, 1 a radio frequency amplifier comprising 50 t e freq of t e Signal to p fi a tube ll having a tank circuit consisting of an e control sign l f i circuit may also es inductance l2 and a variable capacitor l3 consent the deviations injthe mean frequency of an nected t t output, thereof The radio Oscillator so that the mp l s. an element 05 quency signal is supplied to the input of tube II e tuning circuit Lsa oscillator to Stabilize and the amplified signal is derived from coil 14. automatically the operation'of the oscillator. As coupled in any ta manner t i tan e l2, Will become apparent f je h foxtlowing 'd u for being fed to the next succeeding amplifier description, the circuit of the invention may be Stage or to the detector, as in conventional applicable to numerous other uses in the radio ceiver circuits Y and electronicart s,.andthe inventionis n ting Connected in parallel with capacitor I3, is Ended to be hmited to speclfic e ti q en 25 a second variable capacitor, of relatively small dlscloseda W capacitance as compared with capacitor 13, ca-

7 According e bed me th pacitor I5 being periodically varied by a, small invention means d q for Per al motor [6 mechanically coupled, thereto. Motor varying t reactanc 9t. W the nt 9 .,I6 may be of any conventional type and is prefertuned or resonant t t j n' f ably of the two phase type, driyenby analteration results in nating current source l1, there being a "phase output of the resonant gram. a-portlon m shifter l8 interposed between source I1 and one output is utilized as thecontrol potential'for the input of motor '6 in order to supply the proper motor for maintaining the resonant circuit-at its voltages to motor I 6. Motor l 6 periodically varies p m Operating p Having attained this the capacity of capacitor I5 so as to periodically g g qg -i gv g g f fi i f 35 vary the total capacity of the tank circuit, the s a lonalzy unl FY; i frequency f .of this modulation of the total ca- An ob ect of this invention is the provision of f an automatic control'circuit for maintaining a g g g gi fig gg g f g g ggfi g giggz dint ors an e p 1 fi g g 32322;? g i ggmgfi gg g zfigg modulatlondoes notinterfere with the normal sion of an automatic -tuning circuit which is part f g g g f ticularly applicable to remote control operation. cfmple 0 m ance m 0 i A further is t provide an automatic I9, is a detector 2i for detecting the modulations control 'circuit'of hi h control sensitivit impressed on the radio qu y natby gr i g gm t l 1 tig a 1, I n1 pacitor IS, the output of detector 2| being fed Still another object of this invention is the toany Co y em, such'as a Servo system provision of an automatic tuning device which illus r t d s eomprlsmg a s rv amp ifi r 2 a d does not interfere'with the normal operation of a servo motor 23. Motor 23 s drlven y ou the circuit in which it is employed. [1, there being interposedbetween source I! and The exact natureicf this-inventionas well as one input of motor 23, which is preferablyot the two phase type, an adjustable phase shifter 3| for properly adjusting the phase of that input.

Referring now to Fig. 2 there is shown a curve 24 representing the radio frequency output signal across inductance i2, and similarly across coil i9, as a function of the total capacity in the tuned circuit. If it is assumed that the total value of the capacity of the tuned circuit is such that the circuit is operating at point 25 of curve 24 with respect to the frequency of the incoming signal, it is obvious that the capacity of the tjunedcircuit must be increased to bring the amplifier to its optimum operating point, namely point 26 of curve 2%. operation at point 21 would require a decrease in total capacity. Now, assuming that the circuit isoperating a On the other hand, .1

circuit, motivemeans gfor periodically varying the capacity of 'said second condenser to thereby vary the output of said circuit, motive means for Varying the capacity of the variable condenser "of said circuit, and means responsive to the time a displacement of the output of said circuit for point 25, variation in capacity l5by motor 16 outputs 29a, 2%, are of equal amplitude and frequency, 'but are 180 degrees out of phase. On

Similarly, operation controlling the operation of the last-mentioned motive means.

3. A device according to claim 2, wherein said second condenser is of relatively small capacity with respectto, said circuit condenser.

, l. An automatic tuning device for maintaining a resonant circuit at its optimum operating point with respect to the frequency. of a periodically variable signal supplied thereto, said device comprising a variable condenser connected across the circuit, means for periodically varying the capacthe other hand if thetuned 'circuit was oper- ,atin'gat the optimum point with respect to the double the frequency of curves 29 and 29b.

, By arranging detector 2| and amplifier 22 to be responsive only to frequency variations corresponding to curves 29a and 29b, and by utilizfling signal applied to the input thereof, said ing any well-known phase discriminator as the detector, it can be readily seen that the signal supplied to motor 23 will be proper to tune the resonant or tank circuit to its optimum operating point and maintain the circuit at this point.

t is to bev understood that the particular arrangement of the detector and motor control forms no part of this invention and that any well-known arrangement may be utilized. For

example, the control circuit may be of the type illustrated in 'U. S. Patent No. 2,380,947, dated August 7, 1945, to Murray G." Crosby. In this arrangement, the control voltage would be derived fromthe out-put across coil 59. By placing additio'naltank 'circuit condensers on the same sha'ft as capacitor 53, the system ofthe present invention may be applied to multistage amplifiers. any other suitable control arrangement may be: utilized without departing from the spirit and scope of the present invention as defined in the appended claims.

a The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

f wha t' is claimed is: 7

1. In' a radio frequency amplifying network to be amplified, said device-comprising a second variable condenser connected across the circuit ity of said condenser to'thereby vary the output of said circuit, means for varyin one of the elements of saidcircuit, and means responsive to the phasevariations in ,thefoutput of said circuit due to the variations in said condenser for control- .ling the operation of the last-named varying means.

. -5.- "In combination with a parallel resonant circuit, an automatic tuning device for maintaining said circuit at its optimum operating point with respect to ,the frequency of a periodically varydevicecomprising a variable reactance connected acrossthe circuit, meansfor periodically varying controlling the operation of the last-named varying means. 6. In combination with a source ofradio frequency energy and a tunablev load circuit-coupled to said-source, a device for automatically maintaining said circuit at substantial resonance with respect to the frequency of the applied energy,

said-device comprising'means for varying the-frequencyto whichsaidcircuit is tuned, means for tuning said circuit to resonance independently of the first-named means,;and electrical means responsive to the phase variations in the output of said circuit due to the variations in the tuning of said circuit by said first-named means for controlling theoperation of said tuning means.

, 7 .-In combination with a source of electrical energy having a substantially sinusoidal component'and atunable. load circuit having its input end coupled-to saidsource, automatic tun-ing apparatus comprising means coupled to said circuit for varying the frequency to whichsaid circuit is tuned, means for-tuning said circuit to resonance independently of the .{first-named mean andv means coupled to the output end of said circuit and responsive to the time displacement of the sinusoidal component output due to the condenser, means for periodically'varying the Ilvariationsri thest n -ne of s d. c rcuit by Psaid first-named means for controlling the operation of said tuning means.

8. An automatic tuninig device for maintaining a tunable load circuit at resonance with respect to the frequency of a, sinusoidal component of a signal applied to the input of said circuit, said device comprising means for periodically varying the frequency to which said circuit is tuned. means for independently tuning said circuit to resonance, and means coupled to the output end of said circuit and responsive to the time displalcement of the sinusoidal component output due to the variations in the tuning of said circuit by the first-named means for controlling the operation of said tuning means.

ROBERT P. HAVILAND.

2 REFERENCES CITED The following references are of record in th file of this patent:

UNITED STATES PATENTS 10 Number Name Date 2,458,684 Crandell Jan. 11, 1949 2,466,931 Crandell Apr. 12, 1949 

